This application claims priority under 35 USC 119 of Japanese Patent Application No. 2000-47713 filed on Feb. 24, 2000, the entire disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an automatic sheet feed/transfer apparatus having a generally C-shaped, when viewed laterally, sheet path. This automatic sheet feed/transfer apparatus is applicable to, for example, a photocopier, a facsimile machine and an image forming apparatus having a copy function and a facsimile function in order to feed sheets for scanning.
2. Description of the Related Art
An automatic document feeder (ADF) is known in the art, which is incorporated in a photocopier, a facsimile machine or an image forming apparatus having copy and facsimile functions, to feed a document or sheets to a scanner. Usually, a sheet path, which is generally shaped like xe2x80x9cCxe2x80x9d (or turned xe2x80x9cUxe2x80x9d) when viewed laterally, extends in the machine from a sheet feeder to a sheet discharge tray. A plurality of sheet feed rollers are located at appropriate positions along the sheet path. A retard roller is provided to separately feed the sheets one piece at a time and successively. A platen surface or plate is usually located downstream of the turning point of the C-shaped sheet path for the scanning of the sheets. A relatively large sheet feed roller is positioned in the vicinity of the platen plate. The upstream half of the sheet path extends over the downstream half.
The upstream half of the sheet path is defined by an upper frame of the machine and an upper portion of an intermediate frame. The intermediate frame is pivotable. The downstream half of the sheet path is defined by a lower frame of the machine and a lower portion of the intermediate frame. A guide member facing the platen surface is also provided.
The large feed roller near the platen surface is in press-contact with associated front and rear rollers (i.e., press rollers) to guide the sheets appropriately. However, the sheet path downstream of the plate surface has a steep angle so that the sheet feeding does not take place smoothly. This often results in distortion of the scanned image.
Further, if the guide member is fixedly attached to a platen cover (plate for pressing the sheet), a clearance between the platen surface and guide member cannot be maintained to constant due to assembling errors and/or other reasons. As a result, the clearance becomes too large, and therefore the sheet xe2x80x9cflapsxe2x80x9d during the scanning. This degrades quality of the scanned image.
Moreover, roller drives are located along one side of the sheet path so that a stress is concentrated on one side of the retard roller. This causes the sheet to proceed diagonally.
An object of the present invention is to solve the above described problems of the conventional arrangement.
Another object of the present invention is to facilitate replacing/maintenance of a retard roller.
According to a first aspect of the present invention, there is provided an automatic sheet feeding apparatus including lower, intermediate and upper frames to define a sheet path extending from a sheet inlet to a sheet outlet. The sheet path is generally shaped like xe2x80x9cCxe2x80x9d when viewed laterally. The intermediate frame has a pivotable member which can be opened and closed, and a guide member for guiding a sheet passing over a platen surface. The automatic sheet feeding apparatus also includes an elastic member for biasing the guide member on the platen surface from a turning portion of the generally C-shaped sheet path. Therefore, it is possible to maintain a clearance between the platen surface and guide member and prevent the sheet from flapping.
The guide member may be pivotable about a feed roller shaft located upstream of the platen surface with respect to a sheet feeding direction in the apparatus.
According to a second aspect of the present invention, there is provided an automatic sheet feeding apparatus including a generally C-shaped sheet path extending from a sheet inlet to a sheet outlet, a platen surface located downstream of a turning portion of the C-shaped sheet path, a first guide member for guiding a sheet from the sheet inlet to the turning portion of the C-shaped sheet path, a second guide member for guiding the sheet from the turning portion of the C-shaped sheet path to the platen surface, a third guide member for guiding the sheet from the platen surface to the sheet outlet, and drive rollers for feeding the sheet along the sheet path. The drive rollers are rotatably supported by the first, second and third guide members respectively, and at least the first guide member is pivotable about a shaft of the roller which is supported by the first guide roller.
According to a third aspect of the present invention, there is provided an automatic sheet feed apparatus including a generally C-shaped sheet path defined by lower, intermediate and upper frames. The intermediate frame has a pivotable member that can be opened and closed and a guide member for guiding a sheet passing over a platen surface. The pivotable member has a recess to receive a retard roller, which is generally in contact with a separate roller. Since the pivotable member can be opened and closed and the retard roller is removably supported by the pivotable member, replacement and maintenance of the retard roller can be done easily. An elastic member is also located in the recess for exerting an adjustable biasing force directed in a first direction other than a second direction in which the retard roller presses the separate roller. A direction change member is provided for receiving the biasing force from the elastic member in the first direction and transferring the biasing force to the retard roller in the second direction.
The direction change member may have an L shape when viewed laterally, and may be pivotable about the angled point of the L such that the biasing force acts on the vertical portion of the L in the first direction and the retard roller is biased by the horizontal portion of the L in the second direction substantially perpendicular to the first direction. The direction change member may have a through hole in the vertical portion of the L such that a user can access the elastic member to adjust elasticity of the elastic member.
The automatic sheet feed apparatus may further include a drive mechanism located in the recess, and a removable cover extending over the recess for closing the recess and defining part of the sheet path. The automatic sheet feed apparatus may further include at least one first rib for guiding the retard roller in the second direction, and at least one second rib that is integral with the at least one first rib for supporting the direction change member. Both the first and second ribs are positioned in the recess. The automatic sheet feed apparatus may further include a first arm pivotable up and down about one end thereof in the recess for supporting a drive mechanism for the retard roller, and a second arm removably supported at the other end of the first arm opposite for supporting the retard roller such that the second arm can pivot up and down about the other end of the first arm together with the retard roller. The automatic sheet feed apparatus may further include an intermediate shaft supported by the first arm such that the intermediate shaft extends generally perpendicular to a moving direction of the sheet in the sheet path when viewed from the top. Parts of the drive mechanism upstream of the intermediate shaft may be supported by the first arm on one lateral side of the sheet path, and remaining parts of the drive mechanism located downstream of the intermediate shaft until the retard roller may be supported by the first and second arms on the opposite lateral side of the sheet path.
According to a fourth aspect of the present invention, there is provided an automatic sheet feed apparatus including a generally C-shaped sheet path extending from a sheet inlet to a sheet outlet and defined by lower, intermediate and upper flames. The intermediate frame has a pivotable member that can be opened and closed, and a guide member for guiding a sheet passing over a platen surface. The apparatus also includes a sheet discharge roller unit located at the sheet outlet and having a drive roller supported by the lower frame and a driven roller supported by the pivotable member such that the driven roller faces the drive roller and a shaft of the driven roller is rotatably and movably received in a groove formed in the pivotable member. An inlet opening of the groove for receiving the driven roller shaft is smaller than a diameter of the driven roller shaft and has elasticity.
The apparatus may further include a spring located on the opposite side with respect to the drive roller for pressing the driven roller shaft toward the drive roller. When the pivotable member pivots to cause the driven roller to leave the drive roller, the driven roller shaft may move in the groove and a clearance is created between the driven roller shaft and spring. The sheet inlet of the sheet path may be positioned above the sheet outlet, and an upper surface of the pivotable member may define part of the sheet path extending from the sheet inlet and a lower surface of the pivotable member may define part of the sheet path extending to the sheet discharge roller unit.
According to a fifth aspect of the present invention, there is provided an automatic sheet feed apparatus including lower, intermediate and upper frames to define a sheet path extending in a generally C shape when viewed laterally. The intermediate frame has a pivotable member that can be opened and closed and a guide member for guiding a sheet passing over a platen surface, and the pivotable member is a one piece element made from resin. The apparatus also includes a plurality of ribs formed on the sheet path and extending in a sheet feed direction near the sheet inlet and/or outlet. Therefore, the weight of the apparatus can be reduced and movement of the sheets in the sheet feed direction is facilitated.